HAProxy shows backend server is not available while starting service

Hi All,

I am using HAProxy version (1.5.18 2016/05/10) in my Linux server where i have configured frontend and backend HTTPS CA API service. When i start HAProxy service, it gives me “backend appCallToBackend has no server available” error.
Further checked into logs and found below error.
Proxy appCallToBackend started.
Server appCallToBackend/app1 is DOWN, reason: Layer4 connection problem, info: “General socket error (Permission denied)”, check duration: 0ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
Even HAProxy starts service and when i test it with my URL, it gives me HTTP 503 error code which says backend server is not available.

My backend is HTTPS CA API end point, front end is http. Here is my HAProxy.conf.
Can someone please help me to resolve this error? Is it due to HTTPS at backend and throwing error? If so, please guide me to config backend as HTTPS.

HAProxy.config:

global
log 127.0.0.1 local0 info
chroot /var/lib/haproxy
pidfile /var/run/haproxy.pid
maxconn 4000
user haproxy
group haproxy
daemon
stats socket /var/lib/haproxy/stats

defaults
mode http
log global
option httplog
option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
retries 3
timeout http-request 10s
timeout queue 1m
timeout connect 10s
timeout client 1m
timeout server 1m
timeout http-keep-alive 10s
timeout check 10s
maxconn 3000

frontend appCallFromFrontEnd
bind XX.XXX.XX.XX:443
mode http
default_backend appCallToBackend

backend appCallToBackend
balance roundrobin
mode http
server app1 XX.XXX.XX.XX:8444 check ssl verify none

Thanks
Jaimin